A primary or metastatic malignant neoplasm that affects the epididymis. Representative examples include primary epididymal adenocarcinoma and metastatic carcinoma to the epididymis arising from another anatomic site. The disease is Monarch Disease Ontology entry MONDO_0001016 (epididymis cancer). Also known as: cancer of epididymis, malignant epididymal neoplasm, malignant epididymal tumor, malignant epididymal tumour, malignant epididymis neoplasm, malignant neoplasm of epididymis, malignant neoplasm of the epididymis, malignant tumor of epididymis.